System and method for hybrid location in a umts network

ABSTRACT

A system and method for estimating a location of a wireless device receiving signals from plural nodes of a Universal Mobile Telecommunications System (“UMTS”) network. Observed time difference of arrival (“OTDOA”) measurements of signals received by the wireless device are collected and a message is transmitted to a stand alone serving mobile location center (“SAS”), the message including round trip time information, tipping information, and the collected OTDOA measurements. One or more location measurement units (“LMU”) are tasked to determine uplink and downlink signal measurements between the wireless device and ones of the plural nodes as a function of the transmitted message. At the one or more LMUs, range measurements from the wireless device to ones of the plural nodes, uplink time of arrival (“TOA”) measurements, and downlink TOA measurements are determined. A location of the wireless device may then be determined as a function of the uplink and downlink TOA measurements, OTDOA measurements, round trip time information, and range measurements.

RELATED APPLICATIONS

The instant application is related to and co-pending with InternationalPatent Application No. PCT/US2009/052879, entitled, “System and Methodfor Hybrid Location in a CDMA2000 Network,” filed Aug. 5, 2009, theentirety of which is incorporated herein by reference. The instantapplication is related to and co-pending with International PatentApplication No. PCT/US2009/53919, entitled, “System and Method forHybrid Location in a WiMAX Network,” filed Aug. 14, 2009, the entiretyof which is incorporated herein by reference. The instant application isrelated to and co-pending with International Patent Application No.PCT/US2009/52876, entitled, “System and Method for Hybrid Location in anLTE Network,” filed Aug. 5, 2009, the entirety of which is incorporatedherein by reference. The instant application is related to andco-pending with International Patent Application No. PCT/US2009/53909,entitled, “System and Method for Locating a Wireless Device in a WiMAXNetwork Using Uplink Signals,” filed Aug. 14, 2009, the entirety ofwhich is incorporated herein by reference.

BACKGROUND

The location of a mobile, wireless or wired device is a useful andsometimes necessary part of many services. The precise methods used todetermine location are generally dependent on the type of access networkand the information that can be obtained from the device. For example,in wireless networks, a range of technologies may be applied forlocation determination, the most basic of which uses the location of theradio transmitter as an approximation. The Internet Engineering TaskForce (“IETF”) and other standards forums have defined variousarchitectures and protocols for acquiring location information forlocation determination. In one exemplary network, e.g., a Voice overInternet Protocol (“VoIP”) network, a location server (“LS”) may beautomatically discovered and location information retrieved usingnetwork specific protocols.

Other exemplary wireless networks are a World Interoperability forMicrowave Access (“WiMAX”) network and a Long Term Evolution (“LTE”)network. Generally, WiMAX is intended to reduce the barriers towidespread broadband access deployment with standards-compliant wirelesssolutions engineered to deliver ubiquitous fixed and mobile servicessuch as VoIP, messaging, video, streaming media, and other IP traffic.WiMAX enables delivery of last-mile broadband access without the needfor direct line of sight. Ease of installation, wide coverage, andflexibility makes WiMAX suitable for a range of deployments overlong-distance and regional networks, in addition to rural orunderdeveloped areas where wired and other wireless solutions are noteasily deployed and line of sight coverage is not possible.

LTE is generally a 4G wireless technology and is considered the next inline in the GSM evolution path after UMTS/HSPDA 3G technologies. LTEbuilds on the 3GPP family including GSM, GPRS, EDGE, WCDMA, HSPA, etc.,and is an all-IP standard like WiMAX. LTE is based on orthogonalfrequency division multiplexing (“OFDM”) Radio Access technology andmultiple input multiple output (“MIMO”) antenna technology. LTE provideshigher data transmission rates while efficiently utilizing the spectrumthereby supporting a multitude of subscribers than is possible withpre-4G spectral frequencies. LTE is all-IP permitting applications suchas real time voice, video, gaming, social networking and location-basedservices. LTE networks may also co-operate with circuit-switched legacynetworks and result in a seamless network environment and signals may beexchanged between traditional networks, the new 4G network and theInternet seamlessly.

The original version of the standard on which WiMAX is based (IEEE802.16) specified a physical layer operating in the 10 to 66 GHz range.802.16a, updated in 2004 to 802.16-2004, added specifications for the 2to 11 GHz range. 802.16-2004 was updated by 802.16e-2005 in 2005 anduses scalable orthogonal frequency division multiple access (“SOFDMA”)as opposed to the OFDM version with 256 sub-carriers (of which 200 areused) in 802.16d. More advanced versions, including 802.16e, also bringMultiple Antenna Support through MIMO functionality. This bringspotential benefits in terms of coverage, self installation, powerconsumption, frequency re-use and bandwidth efficiency. Furthermore,802.16e also adds a capability for full mobility support. Mostcommercial interest is in the 802.16d and 802.16e standards, since thelower frequencies used in these variants suffer less from inherentsignal attenuation and therefore gives improved range and in-buildingpenetration. Already today, a number of networks throughout the worldare in commercial operation using WiMAX equipment compliant with the802.16d standard.

The WiMAX Forum has provided an architecture defining how a WiMAXnetwork connects with other networks, and a variety of other aspects ofoperating such a network, including address allocation, authentication,etc. It is important to note that a functional architecture may bedesigned into various hardware configurations rather than fixedconfigurations. For example, WiMAX architectures according toembodiments of the present subject matter are flexible enough to allowremote/mobile stations of varying scale and functionality and basestations of varying size. There is, however, a need in the art toovercome the limitations of the prior art and provide a novel system andmethod for locating WiMAX and LTE subscriber stations. While LTEprotocol is being defined in the 3GPP standards as the next generationmobile broadband technology, there is also a need for mobile subscriberor user equipment (“UE”) location in LTE networks for compliance withthe FCC E-911 requirements and for other location based services.

A number of applications currently exist within conventionalcommunication systems, such as those supporting Global System for MobileCommunication (“GSM”), Time Division Multiple Access (“TDMA”), CodeDivision Multiple Access (“CDMA”), Orthogonal Frequency DivisionMultiple Access (“OFDMA”) and Universal Mobile Telecommunications System(“UMTS”) technologies, for which location solutions are needed by mobileunits, mobile stations, UE or other devices and by other entities in awireless network. Examples of such applications may include, but are notlimited to, GSM positioning and assisted global position system(“A-GPS”) positioning. A-GPS adaptable UE may acquire and measuresignals from a number of satellites to obtain an accurate estimate ofthe UE's current geographic position. GPS-based solutions may offerexcellent accuracy, but GPS-based solutions generally suffer from yieldissues in indoor environments or in environments that provide a poorline of sight to the open sky in which to best receive GPS satellitetransmissions. Furthermore, embedding GPS chipsets into UE may also addan associated cost to the manufacturing of the UE and an associated costto A-GPS functionality in the respective communications network.Further, some organizations are hesitant to offer a positioning methodsolely based upon the availability of a satellite network controlled bythe United States government.

There, however, exists a need in the art to locate UMTS, OFDMA or W-CDMAmobile devices to satisfy FCC E-911 regulations as well as to provideLocation Based Services for mobile phone users. The 3GPP UMTS standardoutlines several methods for location including Cell-ID, A-GPS, ObservedTime Difference of Arrival (“OTDOA”), and Uplink Time Difference ofArrival (“U-TDOA”). Cell-ID generally is the simplest method whichprovides coarse positioning of mobile devices based on a known locationof the coverage area centroid of each base station sector. Additionally,A-GPS is a straightforward implementation for network and handsetmanufacturers due to their legacy in CDMA2000 networks. Likewise, U-TDOAis also a straightforward technique for those skilled in the art and hasbeen widely deployed for other air standards. OTDOA, on the other hand,is confronted with significant implementation challenges for networkcarriers, due to the fact that the base station timing relationshipsmust be known, or measured, for this technique to be viable. Forunsynchronized UMTS networks, where the base station timing is notlocked to a common timing source, the 3GPP standard offers thesuggestion that base station Location Measurement Units (“LMUs”) orNetwork Synchronization Units (“NSUs”) may be utilized to recover thistiming information. Once the base station timing relationships aremeasured, the handset measurements of Observed Time Difference (“OTD”)between various base stations may be translated into absolute ranges andrange differences from which position can be calculated (e.g., throughUE-based or UE-assisted methods).

Network carriers, however, appear to have little interest inimplementing the OTDOA solution. This may be due to a general lack ofcost-effective solutions for practical implementations of OTDOA inunsynchronized UMTS networks, significant hardware, installation,testing, and associated maintenance costs, and/or a lack of availableLMU or NSU vendors. Further, the lack of interest by network carriers inimplementing the OTDOA solution may also be due to a lack of handsetmanufacturers implementing OTDOA measurements into the associatedfirmware, negative perception of OTDOA due to the potential networkcapacity impacts if Idle Period Downlink (“IPDL”) is enabled bycarriers, and/or carrier perception that A-GPS handsets will meet allthe location needs of its users.

The UMTS standard offers alternative location solutions for UE location.OTDOA technologies, with or without IPDL, have been developed andintegrated into the UMTS standard as optional features to enablelocation of UEs. However, UMTS carriers have been reluctant to adoptthese technologies because carriers had not initially requested theseoptional features in most UE devices. Additionally, concern may existregarding the impact OTDOA may have on the operation of a communicationsnetwork including call quality and network capacity. Because widespreadadoption of OTDOA may require modifications in both the base stationsand mobile stations, network providers are generally more interested ina solution that operates with existing mobile devices and base stations.

In a network-based geolocation system, the mobile appliance to belocated is typically identified and radio channel assignments determinedby, for example, monitoring the control information transmitted on aradio channel for telephone calls being placed by the mobile applianceto detect calls of interest, e.g., 911 calls, or a location requestprovided by a non-mobile appliance source, i.e., an enhanced servicesprovider. Once a mobile appliance to be located has been identified andradio channel assignments determined, the location determining system istasked to determine the geolocation of the mobile appliance, and reportthe determined position to an appropriate entity, such as a mobile callcenter or enhanced services provider.

Some prior art systems are mobile appliance-based and determine theposition of the mobile appliance by receiving multiple dedicatedlocation signals either from components outside the mobile appliance'scommunication system, such as satellites and GPS systems or from anetwork of dedicated land-based antennas. Other prior art geolocationsystems that are network overlay, or infrastructure-based, systems usecombinations of specific, as opposed to ambiguous, measurementsgenerally from multiple base stations, such as AOA, TOA and TDOA. Thesespecific measurement values may be utilized to solve a set ofmathematical equations to determine the location of the mobileappliance.

Some prior art systems may rely on determining a channel assignment bymonitoring the control information transmitted on a radio channel fortelephone calls being placed by the mobile appliance to thereby detectcalls of interest or a location request provided by a non-mobileappliance source, e.g., an enhanced services provider. In either case,the identification of the mobile user and its channel assignmentnecessitate retrieval of information bits from the mobile appliance,through control signals or call setup information. However with theadvent of the third generation CDMA specification known in the art asCDMA2000, a new system and method can be used to determine the locationof a mobile appliance independent of the information data bitstransmitted by the mobile appliance. In a system operating under theIS-95 standard, the forward link uses the pilot, paging, and synccontrol channels to maintain the link while the forward traffic channelis used for data and voice communication. On the reverse link, themobile access channel is used to gain access to the system and thetraffic channel is used for data and voice transfer. In a systemoperating under the CDMA2000 IS-2000 standard, the IS-95 forward linkchannels are used in addition to a dedicated reverse pilot channel fromthe mobile appliance to the base station. The reverse pilot signal isunique for each mobile appliance and is typically a function of theElectronic Serial Number (“ESN”). The reverse pilot signal generallyidentifies the mobile appliance and typically incorporates a timereference so subsequent data sent by the mobile appliance may be decodedat the base station. The reverse pilot channel typically is used, forexample, for coherent demodulation, multi-source combining, andidentification of a mobile appliance. For IS-95 systems, a networkoverlay geolocation system for geolocating a mobile appliance typicallyentails transferring a large amount of information through thegeolocation system in order to geolocate a mobile appliance. As is knownin the art, the ESN of a mobile appliance may typically be determinedfrom a location requesting entity, from control channels, from certainsignaling present in the wired portion of the wireless communicationsystem, or other such methods. Details of the reverse pilot signal in aCDMA2000 wireless communication system are established by theTelecommunications Industry Association (“TIA”), and the existence ofthe reverse pilot channel in IS-2000 communication systems presents aresource for efficiently geolocating a mobile appliance.

Therefore, there is a need in the art to utilize the characteristics ofthe reverse pilot channel in creating a system and method forgeolocating a mobile appliance operating in a wireless communicationsystem under the CDMA2000 specifications. To obviate the deficiencies inthe prior art one embodiment of the present subject matter provides ahybrid mobile location method that uses both uplink and downlink signalmeasurements in an exemplary communications network, such as, but notlimited to, a WiMAX, UMTS, CDMA2000, and/or LTE network.

One embodiment of the present subject matter provides a method forestimating a location of a wireless device receiving signals from pluralnodes of a WiMAX communication system. The method may comprisedetermining downlink signal measurements including a range of thewireless device from a serving node, an OTDOA measurement of a signalfrom one or more neighboring nodes, and a transmission time of thesignal from the one or more neighboring nodes. The method may furtherinclude determining uplink signal measurements including a TOAmeasurement of a ranging signal from the wireless device, and a timingadjust parameter of the wireless device. A location of the wirelessdevice may then be estimated as a function of the determined downlinkand uplink signal measurements.

Another embodiment of the present subject matter may provide a methodfor estimating a location of a wireless device receiving signals fromplural nodes of a WiMAX communication system. The method may comprisedetermining downlink signal measurements of first signals received bythe wireless device from the plural nodes, and transmitting a secondsignal from at least one of the plural nodes to the wireless device. Athird signal may be transmitted from the wireless device in response tothe second signal, and uplink signal measurements determined as afunction of the third signal. A location of the wireless device may thenbe estimated as a function of the determined downlink and uplinkmeasurements.

A further embodiment of the present subject matter provides a system forestimating a location of a wireless device receiving signals from aplurality of nodes of a communication system. The system may includecircuitry for determining downlink signal measurements of first signalsreceived by the wireless device from the plural nodes and a transmitterfor transmitting a second signal from at least one of the plural nodesto the wireless device. The system may also include a receiver forreceiving a third signal transmitted from the wireless device inresponse to the second signal and circuitry for determining uplinksignal measurements as a function of the third signal. The system mayinclude circuitry for estimating a location of the wireless device as afunction of the determined downlink and uplink measurements.

One embodiment of the present subject matter provides a method forestimating a location of a wireless device receiving signals from pluralnodes of a communications network. The method comprises directing awireless device to transmit a first signal having one or morepredetermined parameters, transmitting the first signal by the wirelessdevice, and determining at one or more LMUs an uplink TOA measurementbetween the wireless device and one or more of the plural nodes or LMUsas a function of the transmitted first signal. Downlink signalmeasurements of signals received by the wireless device may be collectedand a location of the wireless device determined as a function of theuplink TOA measurements and the collected downlink signal measurements.

Another embodiment of the present subject matter provides a method forestimating a location of a wireless device receiving signals from pluralnodes of a communications network. The method comprises directing awireless device to transmit a sounding reference signal (“SRS”) ordemodulation reference signal (“DMRS”) with one or more predeterminedparameters, and transmitting the SRS or DMRS signal by the wirelessdevice. An uplink TOA measurement between the wireless device and one ormore of the plural nodes or LMUs may be determining at the LMUs as afunction of the transmitted signal, and a location of the wirelessdevice determined as a function of the uplink TOA measurement.

A further embodiment of the present subject matter provides a method forestimating a location of a wireless device receiving signals from pluralnodes of an LTE communications network. The method comprises directing awireless device to transmit a first signal having one or morepredetermined parameters and transmitting the first signal by thewireless device. A range of the wireless device from a node serving thewireless device may be determined as a function of information in thetransmitted first signal. This determination may comprise determining atiming adjustment from signals transmitted by said serving node,receiving the transmitted first signal transmitted by the wirelessdevice at a reference station, correlating the received first signalwith a reference signal, determining time of arrival information fromthe correlated signal, and determining a range of the wireless devicefrom one or more of the plural nodes as a function of one or more of thetime of arrival and timing adjustment information. A location of thewireless device may then be determined as a function of the determinedrange.

One embodiment of the present subject matter provides a method forestimating a location of a wireless device receiving signals from pluralnodes of a UMTS network. The method comprises collecting OTDOAmeasurements of signals received by the wireless device, andtransmitting a message to a standalone serving mobile location center(“SAS”), the message including round trip time information, tippinginformation, and the collected OTDOA measurements. One or more LMUs maybe tasked to determine uplink and downlink signal measurements betweenthe wireless device and ones of the plural nodes as a function of thetransmitted message. Range measurements from the wireless device to onesof the plural nodes, uplink TOA measurements, and downlink TOAmeasurements may then be determined at one or more LMUs, a location ofthe wireless device estimated as a function of the uplink and downlinkTOA measurements, OTDOA measurements, round trip time information, andrange measurements.

An additional embodiment of the present subject matter provides a systemfor estimating a location of a wireless device. The system may includecircuitry for collecting OTDOA measurements of signals received by thewireless device, a transmitter for transmitting a message includinground trip time information, tipping information, and the collectedOTDOA measurements, and circuitry for tasking one or more LMUs toperform uplink and downlink signal measurements between the wirelessdevice and ones of plural nodes as a function of the transmittedmessage. The system may also include circuitry at the one or more LMUsfor performing range measurements from the wireless device to ones ofthe plural nodes, uplink TOA measurements, and downlink TOAmeasurements, and circuitry for estimating a location of the wirelessdevice as a function of the uplink and downlink TOA measurements, OTDOAmeasurements, round trip time information, and range measurements.

Another embodiment of the present subject matter provides a system andmethod for estimating a location of a wireless device receiving signalsfrom plural nodes of a Code Division Multiple Access 2000 communicationssystem. One or more ranges of a wireless device from one or more of theplural nodes may be determined as a function of signals received at thewireless device from the respective one or more plural nodes and as afunction of information in an uplink pilot signal. From one or morelocation measurement units (“LMU”) measurements an uplink time ofarrival (“TOA”) measurement from the device may be determined and thenan estimation of the location of the wireless device determined as afunction of the uplink TOA and determined one or more ranges.

These embodiments and many other objects and advantages thereof will bereadily apparent to one skilled in the art to which the inventionpertains from a perusal of the claims, the appended drawings, and thefollowing detailed description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the present disclosure will be or become apparent toone with skill in the art by reference to the following detaileddescription when considered in connection with the accompanyingexemplary non-limiting embodiments.

FIG. 1 is a diagram of an exemplary access network model.

FIG. 2 is a high level diagram of one embodiment of the present subjectmatter.

FIG. 3 is a more detailed diagram of an exemplary WiMAX Location BasedService network architecture.

FIG. 4 is a diagram illustrating one method for hybrid signal basedlocation in a WiMAX network.

FIG. 5 is a diagram of another embodiment of the present subject matter.

FIG. 6 is a diagram of one embodiment of the present subject matter.

FIG. 7 is a diagram illustrating one method for hybrid signal basedlocation in a Universal Mobile Telecommunications System (“UMTS”)network.

FIG. 8 is a diagram illustrating another method for uplink and downlinksignal based location in a network employing UMTS technologies.

FIG. 9 is a sequence diagram of one embodiment of the present subjectmatter.

FIG. 10 is a sequence diagram of another embodiment of the presentsubject matter.

FIG. 11 is a diagram of another embodiment of the present subjectmatter.

FIG. 12 is a diagram of a further embodiment of the present subjectmatter.

FIG. 13 is a diagram of one embodiment of the present subject matter.

FIG. 14 is an illustration of one embodiment of the present subjectmatter.

FIG. 15 is a diagram of another embodiment of the present subjectmatter.

FIG. 16 is an illustration of an exemplary hybrid location techniqueaccording to one embodiment of the present subject matter.

DETAILED DESCRIPTION

With reference to the figures where like elements have been given likenumerical designations to facilitate an understanding of the presentsubject matter, the various embodiments of a system and method forhybrid location in a UMTS network are herein described.

Embodiments of the present subject matter may provide handsets capableof OTDOA measurements, network support of OTDOA measurements, GPStrained LMUs deployed in the network, network support of providinguplink tipping information and OTDOA measurements to a serving mobilelocation center (“SMLC”).

Generally, a WiMAX or LTE subscriber or mobile station may provide to acommunications network round trip delay (“RTD”) information of an anchorbase station's downlink and uplink signals and the observed relativedelays of the neighboring base stations' downlink and uplink signals.The phrases subscriber station, mobile station, mobile appliance,wireless device, and user equipment (“UE”) are used interchangeablythroughout this document and such should not limit the scope of theclaims appended herewith. Further, the terms station and device are alsoused interchangeably throughout this document and such should not limitthe scope of the claims appended herewith. The respective WiMAX or LTEnetwork may utilize this data for hand-off operations; however,embodiments of present subject matter may determine from this data arange ring from the anchor or serving base station (“BS”) or node andlocation hyperbolas between the reported BSs, if the BS timings areknown.

In one embodiment of the present subject matter, an exemplary system mayinclude a location server (“LS”), such as a Location Information Server(“LIS”), which is generally a network server that provides devices withinformation about their location. Devices that require locationinformation may be able to request their location from the LS. In thearchitectures developed by the IETF, NENA and other standards forums,the LS may be made available in an IP access network connecting one ormore target devices to the Internet. In other modes of operation, the LSmay also provide location information to other requesters relating to atarget device.

To determine location information for a target device, an exemplary LSmay utilize a range of methods. The LS may use knowledge of networktopology, private interfaces to networking devices like routers,switches and base stations, and location determination algorithms.Exemplary algorithms may include known algorithms to determine thelocation of a mobile device as a function of satellite information,satellite assistance data, various downlink or uplink algorithms suchas, but not limited to, time difference of arrival (“TDOA”), time ofarrival (“TOA”), angle of arrival (“AOA”), round trip delay (“RTD”),signal strength, advanced forward link trilateration (“AFLT”), enhancedobserved time difference (“EOTD”), observed time difference of arrival(“OTDOA”), uplink-TOA and uplink-TDOA, enhanced cell/sector and cell-ID,etc., and hybrid combinations thereof.

FIG. 1 is a diagram of an exemplary access network model. With referenceto FIG. 1, an exemplary access network model 100 may include one or moreLSs 102 connected to one or more access networks, 110-170. An accessnetwork refers to a network that provides a connection between a deviceand the Internet. This may include the physical infrastructure, cabling,radio transmitters, switching and routing nodes and servers. The accessnetwork may also cover services required to enable IP communicationincluding servers that provide addressing and configuration informationsuch as DHCP and DNS servers. Examples of different types of accessnetworks include, but are not limited to, DSL 110, cable 120, WiFi,wired Ethernet 130, WiMAX 140, cellular packet services 150, and 802.11wireless 160, LTE 170, among others. An exemplary LS 102 may beimplemented on multiple processing units, any one of which may providelocation information for a target device from a first site, a secondsite and/or additional sites. Therefore, an exemplary LS 102 may providehigh availability by having more than one processing unit at a firstsite and by having multiple processing units at a second site forcopying or backup purposes in the event a site or a processing unitfails.

FIG. 2 is a high level diagram of one embodiment of the present subjectmatter. With reference to FIG. 2, an exemplary wireless network orsystem 200 may include an LS 202 in communication with one or more basestations (“BS”) 222, a positioning determining entity (“PDE”) 232, oneor more network synchronization units (“NSU”) 242 and one or morelocation measurement units (LMUs) (not shown). One or more mobile orsubscriber stations or devices 210 may be in communication with the LS202 via the one or more BSs 222. A recipient or user 212 of locationinformation may request the LS 202 to locate a subscriber station 210.The LS 202 may then request the serving BS 222 to provide networkmeasurement information. The BS 222 receives the data from the targetsubscriber station 210 and provides the data to the LS 202. The LIS 202may, in one embodiment, send the data to the PDE 232 to compute thelocation of the target station or device 210. Once the location iscomputed, the LS 202 may provide the location information to therequesting user 212.

FIG. 3 is a more detailed diagram of an exemplary WiMAX Location BasedService (“LBS”) network architecture 300. With reference to FIG. 3, theWiMAX forum defines a number of functional entities and interfacesbetween those entities. An exemplary network architecture 300 includesone or more access service networks (“ASN”) 320, each having one or morebase stations (“BS”) 322, 323 and one or more ASN gateways (“ASN-GW”)324 forming the radio access network at the edge thereof. One or moremobile stations or devices 310, such as a WiMAX device, having alocation requester 312 may be in communication with the ASN 320 via oneor more BSs 322, 323 over an R1 interface 301. BSs 322, 323 areresponsible for providing the air interface to the device 310.Additional functions may, of course, be part of BSs 322, 323, such asmicromobility management functions, handoff triggering, tunnelestablishment, radio resource management, QoS policy enforcement,traffic classification, Dynamic Host Control Protocol (“DHCP”) proxy,key management, session management, and multicast group management, toname a few. BSs 322, 323 communicate with one another via residentlocation agents (“LA”) 325 over an R8 interface 308. LAs 325 aregenerally responsible for measurements and reporting and may communicatewith the device 310 to collect measurements. BSs 322, 323 alsocommunicate with the ASN-GWs 324 via a location controller (“LC”) 326 inthe ASN-GW 324 over an R6 interface 306. LCs 326 generally trigger andcollect location measurements and forward these measurements to an LS ina selected connectivity service network (“CSN”) 330.

The ASN-GW 324 generally acts as a layer 2 traffic aggregation pointwithin an ASN 320. Additional functions that may be part of the ASN-GW324 include, but are not limited to, intra-ASN location management andpaging, radio resource management and admission control, caching ofsubscriber profiles and encryption keys, AAA client functionality,establishment and management of mobility tunnel with BSs, QoS and policyenforcement, foreign agent functionality for mobile IP and routing to aselected CSN. Communication between ASNs 320 occurs over an R4 interface304. It should also be noted that a Public Safety Answering Point(“PSAP”) or an Internet Application Service Provider (“iASP”) 340 mayalso include a location requester 342 and may be in communication with ahome CSN 334 over a U1 interface 344. The U1 interface 344 may also bein communication with a visited CSN (“V-CSN”) 332 and hence the visitedlocation server and communication from the applications (PSAPs included)may be to either the visited or the home location servers.

A third portion of the network includes the CSN 330. The CSN may be avisited network having a V-CSN 332 or a home network having a home-CSN(“H-CSN”) 334, collectively CSNs 330. These CSNs 330 provide IPconnectivity and generally all the IP core network functions in thenetwork 300. For example, the CSN 330 provides connectivity to theInternet, ASP, other public networks and corporate networks. The CSN 330is owned by a network service provider (“NSP”) and includesAuthentication Authorization Access (“AAA”) servers (home-AAA 338 andvisited-AAA 339 servers) that support authentication for the devices,users, and specific services. The CSN 330 also provides per user policymanagement of QoS and security. The CSN 330 is also responsible for IPaddress management, support for roaming between different NSPs, locationmanagement between ASNs 320, and mobility and roaming between ASNs 320,to name a few. Communication between the ASN 320 and a CSN 330 occursvia the respective ASN-GW 324 over an R3 interface 303.

One entity within a CSN 330 is an LS. Depending upon whether the device310 is roaming and in direct communication with a remote network or indirect communication with a home network, the LS may be a visited-LS(“V-LS”) 336 or a home-LS (“H-LS”) 337. The role of the LS is to providelocation information about a WiMAX device 310 in the network 300.Communication between the WiMAX device 310 and the LS 336, 337 isperformed over an R2 interface 302.

It should be noted that there are several location determination methodssupported by the above-described network architecture 300. For example,a location server may utilize 802.16m MAC and PHY features to estimate alocation of a mobile appliance when GPS is not available via an R2interface, e.g., indoors, or be able to faster and more accuratelyacquire GPS signals for location determination. The network 300 may makethe GPS assistance data, including GPS Almanac data and Ephemeris data,available to the device 310 using the R2 interface and HELD or SUPL.

Non-GPS-Based supported methods may rely on the role of the serving andneighboring BSs or other components. For example, in a downlink (“DL”)scenario, a device 310 may receive existing signals (e.g., preamblesequence) or new signals designed specifically for the LBS measurements,if it is needed to meet the requirement from the serving/attached BS andmultiple neighboring BSs 322, 323. The BSs 322, 323 are able tocoordinate transmission of their sequences using different time slots ordifferent OFDM subcarriers. The device 310 may accurately determine therequired measurements, even in the presence of multipath channel andheavy interference environment, and then estimate its locationaccordingly. In an uplink (“UL”) scenario, various approaches may beutilized at the BSs 322, 323 to locate the device. Exemplarymeasurements are generally supported via existing UL transmissions(e.g., ranging sequence) or new signals designed specifically for theLBS measurements. Exemplary methods may include but are not limited to,TDOA, TOA, RTD, AOA, RSSI, Advanced forward link trilateration(“A-FLT”), Enhanced observed time difference (“EOTD”), Observed timedifference of arrival (“OTDOA”), time of arrival (“TOA”), uplink-TOA anduplink-TDOA, Enhanced cell/sector and cell-ID, etc., and hybridcombinations thereof.

For example, in one embodiment of the present subject matter, a BS 322,323 may transmit a signal, such as a Fast_Ranging_IE signal, to a mobiledevice or station 310 and the mobile station 310 may transmit anothersignal, such as a ranging signal, in response thereto. If thecharacteristics of the ranging signal are known to components of thenetwork, such as an LMU, then the uplink signal TOA may be determined.Therefore, as the serving BS receives the ranging signal, the serving BSmay measure the uplink transmission timing adjustment that provides therange of the mobile station 310 from the respective BS. While uplinkmeasurements are being performed, an exemplary downlink OTDOA locationmethod may also be invoked, and therefore, both uplink and downlinkmeasurements may be utilized to determine a location of the mobilestation 310.

FIG. 4 is a diagram illustrating one method for hybrid signal basedlocation in a WiMAX network. With reference to FIG. 4, a location server(“LS”) 450 may at step 401 transmit a request for network assistance toa BS 452. At step 402, the mobile station 454 may perform OTDOAmeasurements and send such measurements to the BS 452 or other networkcomponents. These OTDOA measurements may then be provided to the LS atstep 403. One exemplary downlink OTDOA location technique is describedin further detail in co-pending U.S. application Nos. 61/055,658 and12/104,250, the entirety of each are incorporated herein by reference.These OTDOA measurements may be performed independently of any of theidentified steps in FIG. 4.

In step 404, the BS 452 may transmit ranging related parameters to amobile station 454. For example, the BS 452 may transmit allocations fornon-contention based ranging to the MS 454. This may be performedutilizing a UL-MAP IE signal and/or UCD. The parameters of a UL-MAP IEsignal are described in section 8.4.5.4, table 287 of IEEE Std.802.16e-2005 and the parameters of UCD are described in section 11.3.1,table 353 of the same, the entirety of each are incorporated herein byreference. In one embodiment, the BS 452 may allocate the rangingopportunity sufficiently ahead of actual transmission time so that LMUs456 in the respective network may possess adequate time to tune to theuplink signal and collect samples prior to transmission of a rangingsignal from the MS 454. If, however, sufficient allocation of a rangingopportunity is not possible, the LMUs 456 may continuously collect andsave baseband samples in a circular buffer. Tipping information may betransmitted from the BS 452 to the LS 450 and then to the LMUs 456 insteps 405 and 406. Once tipping information arrives at the LMU 456, theLMUs 456 may search for the TOA of a ranging signal in previously storeddata.

LMU tipping information is generally a set of parameters that defines aranging signal transmitted by an MS 454. An LMU 456 may utilize tippinginformation to recreate the transmitted signal by the MS 454. Table 1below provides a non-exhaustive list of exemplary tipping informationfor uplink measurement based location.

TABLE 1 Parameter Name Comment CID UL-MAP IE, section 8.4.5.4, table 287of IEEE Std. 802.16e−2005. Serving BSID Identifier for the serving BSOFDMA UL-MAP IE, section 8.4.5.4, table 287 of IEEE Std. symbol offset802.16e−2005. Subchannel offset UIUC, section 8.4.5.4.3 of IEEE Std.802.16e−2005. No. OFDMA symbols No. subchannels Ranging method Dedicatedranging indicator CDMA_ UL-MAP IE, section 8.4.5,4, table 287 of IEEEStd. Allocation_IE 802.16e−2005. UIUC = 12, section 8.4.5.4.3 of IEEEStd. 802.16e−2005. Fast_Ranging_IE UL-MAP IE, UIUC = 15, Section8.4.5.4.21 of IEEE Std. 802.16e−2005. Permutation base Section 11.3.1,Table 353 of IEEE (UL_PermBase) Std. 802.16e−2005. Action time Section6.3.2.3.52, Table 109 of IEEE Std. 802.16e−2005. Approximate Thisparameter may be derived from other parameters ranging signal such as,but not limited to, approximate clock of the transmission time basestation, allocation start time, duration of the allocation, etc. Section10.3.4.1 and table 342 of IEEE Std. 802.16e−2005.

The parameters listed above in Table 1 are generally dynamic; however,LMUs 456 may also utilize any one or combination of the followingsemi-static parameters: the BS identity of the base stations, thelocation of any one of the BSs, the azimuth of the base station sectorantennas, downlink preamble sequence of each BS, system bandwidth,sampling frequency, FFT size, etc. These semi-static parameters may beperiodically passed to an LS as system log files.

With continued reference to FIG. 4, at step 407, a BS 452 such as aserving BS may transmit a signal, such as but not limited to aFast_Ranging_IE signal, to the MS 454 to trigger the transmission of theranging signal. In response, at step 408 the MS 454 may transmit aranging signal. The ranging signal may be received by any of the BSs452, serving or neighboring base stations and/or the LMUs 456. Theserving BS 452 may then transmit at step 409 another message or signal,such as a MOB_ASC-REP message, including timing adjust parameters forthe BSs 452 that detected the ranging signal. The MOB_ASC-REP messagemay be transmitted with the ranging results from the serving BS 452. TheLMUs 456 may then determine the uplink TOAs of the ranging signal andsend the TOA values to the LS at step 410. At step 411, the location ofthe MS 454 may then be determined utilizing any one or combination of anOTDOA of a neighboring BS's downlink signal, a range of the MS from theserving BS (e.g., from OTDOA measurements), a downlink transmission timeof the neighboring BSs as measured by the LMU, the uplink TOA of theranging signal as measured by the LMU, and/or timing adjust of the MS.

FIG. 5 is a diagram of another embodiment of the present subject matter.With reference to FIG. 5, a method 500 is provided for estimating alocation of a wireless device receiving signals from plural nodes of aWiMAX communication system. These nodes may be base stations, basestation sectors, and combinations thereof. At step 510, downlink signalmeasurements may be determined which include a range of the wirelessdevice from a serving node, an OTDOA measurement of a signal from one ormore neighboring nodes, and a transmission time of the signal from theone or more neighboring nodes. At step 520, uplink signal measurementsmay be determined which include a TOA measurement of a ranging signalfrom the wireless device, and a timing adjust parameter of the wirelessdevice. Of course, the downlink signal measurements may be determinedindependently of the uplink signal measurements in one embodiment. Atstep 530, a location of the wireless device may then be estimated as afunction of the determined downlink and uplink signal measurements.

FIG. 6 is a diagram of another embodiment of the present subject matter.With reference to FIG. 6, a method 600 is provided for estimating alocation of a wireless device receiving signals from plural nodes of aWiMAX communication system. These nodes may be base stations, basestation sectors, and combinations thereof. Exemplary wireless devicesmay be, but are not limited to, a cellular device, text messagingdevice, computer, portable computer, vehicle locating device, vehiclesecurity device, communication device, and wireless transceiver. Themethod may include, at step 610, determining downlink signalmeasurements of first signals received by the wireless device from theplural nodes, and at step 620 transmitting a second signal from at leastone of the plural nodes to the wireless device. Exemplary downlinksignal measurements may include one or more of a range of the wirelessdevice from a serving node, an OTDOA measurement of a signal from one ormore neighboring nodes, a transmission time of the signal from the oneor more neighboring nodes, and combinations thereof. An exemplary secondsignal may be, but is not limited to, a Fast_Ranging_IE signal. In oneembodiment, step 610 may include determining an OTDOA hyperbola usinginformation received from a network measurement report (“NMR”).

At step 630, a third signal may be transmitted from the wireless devicein response to the second signal, and uplink signal measurementsdetermined as a function of the third signal at step 640. Exemplaryuplink signal measurements may include one or more of a TOA measurementof a ranging signal from the wireless device, a timing adjust parameterof the wireless device, and combinations thereof. Further, the downlinksignal measurements may be determined independently of the uplink signalmeasurements in one embodiment. At step 650, a location of the wirelessdevice may be determined as a function of the determined downlink anduplink measurements. In one embodiment, the method 600 may furtherinclude the steps of transmitting allocations for non-contention basedranging to the wireless device and transmitting tipping information toone or more LMUs. This transmission of tipping information may includerecreating signals transmitted by the wireless device as a function ofinformation selected from the group consisting of: connection identifier(“CID”), base station identifier (“BSID”), azimuth of base stationsector antennas, downlink preamble sequence of base stations, systembandwidth, sampling frequency, fast-Fourier transformation size,orthogonal frequency division multiple access (“OFDMA”) symbol offset,sub-channel offset, number of OFDMA symbols, number of sub-channels,ranging method, dedicated ranging indicator, CDMA_Allocation_IEparameter, Fast_Ranging_IE parameter, Permutation base, action time,approximate ranging signal transmission time, and combinations thereof.Another embodiment may also include the step of transmitting a requestfor network assistance to locate the wireless device to at least one ofthe plural nodes.

FIG. 7 is a diagram illustrating one method for hybrid signal basedlocation in a Universal Mobile Telecommunications System (“UMTS”)network. With reference to FIG. 7, a Serving Radio Network Controller(“SRNC”) 710 may receive a request for network assistance to locate awireless device or UE 720 at step 701. This request may be provided by aStand Alone SMLC (“SAS”) 730 or other entity. The SRNC 710 may collectthe UE's OTDOA measurements at step 702 and transmit these measurements,for example, as a POSITION CALCULATION REQUEST message, to the SAS atstep 703. A POSITION CALCULATION REQUEST message may contain round triptime information, OTDOA measurements, and uplink tipping information.See sections 9.2.2.31, 9.2.2.32, 9.2.2.33, 9.2.2.34 and 9.2.2.74 of 3GPPTS 25.453 V7.6.0 (2007-03) the entirety of which are incorporated hereinby reference. After the SAS 730 receives the transmitted message orPOSITION CALCULATION REQUEST message, the SAS 730 may task LMUs 740 inthe system to make the uplink and downlink measurements at step 704 as afunction of tipping information. The LMUs 740 may then provide uplinkTOAs, downlink TOAs, and UE range estimates to the SAS 730 at step 705.The SAS or any position determination equipment (“PDE”) thereof may thendetermine the location of the UE 720 using any one or combination ofthese downlink TOAs, downlink OTDOAs, uplink TOAs, and range estimatesat step 706.

FIG. 8 is a diagram illustrating another method for uplink and downlinksignal based location in a network employing UMTS technologies. Withreference to FIG. 8, at step 810 OTDOA measurements of signals receivedby a wireless device may be collected and at step 820, a messageincluding round trip time information, tipping information, and thecollected OTDOA measurements may be transmitted to a SAS. The wirelessdevice may be, but is not limited to, but are not limited to, a cellulardevice, text messaging device, computer, portable computer, vehiclelocating device, vehicle security device, communication device, andwireless transceiver. In one embodiment, step 810 may further includedetermining an OTDOA hyperbola using information received from an NMR.In another embodiment, step 810 may include determining ranges fromserving and/or neighboring base stations. At step 830 one or more LMUsmay be tasked to determine uplink and downlink signal measurementsbetween the wireless device and ones of plural nodes in the network as afunction of the transmitted message. These nodes may be, but are notlimited to, base stations, base station sectors, radio networkcontrollers, serving radio network controllers, and combinationsthereof. At the one or more LMUs, range measurements from the wirelessdevice to ones of the plural nodes, uplink TOA measurements, anddownlink TOA measurements may be determined at step 840. In oneembodiment of the present subject matter, the range measurements may bedetermined as a function of a UE Rx-Tx time difference.

A location of the wireless device may then be estimated at step 850 as afunction of the uplink and downlink TOA measurements, OTDOAmeasurements, round trip time information, and range measurements. Inone embodiment of the present subject matter, the step of collectingOTDOA measurements and the determination of uplink TOA measurements maybe conducted substantially simultaneously. For example, the SRNC maytransmit uplink tipping information to the SAS as the SRNC collectsdownlink OTDOA measurements from the UE. The PDE may then determine alocation for the UE when both uplink and downlink measurements areavailable. Therefore, in one embodiment of the present subject matter,an exemplary GCS may have the following measurements for locationcomputation: relative time difference of arrival of neighboring basestations' downlink signal, range of the UE from the serving BS (fromround trip time information), uplink TOA as measured by the LMU,downlink TOA as measured by the LMU, and/or range of the UE from theserving site as measured by the LMU. In another embodiment of thepresent subject matter, the method may include transmitting a requestfor network assistance to at least one of the plural nodes to locate thewireless device.

Embodiments of the present subject matter may also be utilized innetworks employing LTE technologies. As discussed above, LTE isgenerally directed toward a packet-optimized IP centric framework and isexpected that voice calls will be transported through VoIP and locationrequests, e.g., E-911, etc., will also be serviced through VoIP. In LTEnetworks, mobile appliances or devices may be transmitting to an e-NodeBor other access node or femtocell through various physical channels.Uplink timing measurements may be conducted as a function of SoundingReference Signal (“SRS”) or Demodulation Reference Signal (“DMRS”)sequences. Generally, the SRS is transmitted by a UE for channel qualityassessment and the DMRS is transmitted with and covers the samefrequency allocation as the corresponding physical channel. If any oneor several LMUs in a respective network is tipped with propercharacteristics of these signal sequences, an uplink signal TOA may bedetermined. Further, the serving node may acquire the timing adjustmentof the UE which may thus provide a range of the UE from the e-NodeB. Alocation of the UE may then be determined as a function of the TOAinformation from the LMUs and range information from the servinge-NodeB. In another embodiment of the present subject matter, OTDOAmeasurements may be performed by the UE during LMU uplink TOAmeasurement performance. Thus, uplink and downlink measurements may thenbe combined to increase the yield and accuracy of a locationdetermination of the UE.

FIG. 9 is a sequence diagram of one embodiment of the present subjectmatter. With reference to FIG. 9, in response to a location servicerequest, a UE 960 may be directed to generate SRS signals with specificperiodicity, power, bandwidth and frequency position. LMUs 920 in thenetwork may be tipped with any or all the characteristic tippinginformation of the SRS as provided in Table 2 below from an e-SMLC 930or GCS. The LMU 920 may thus determine uplink TOA information bydetecting the SRS signal at the LMU 920. It should be noted that FIG. 9assumes that there is no direct interface between an e-NodeB 950 and thee-SMLC/SMLC 930. Data may be passed through a Mobility Management Entity(“MME”) 940 thereby using the MME 940 as a proxy server. Of course, theMME 940 provides additional functionality as a control-node for an LTEnetwork. Generally, the MME 940 may be responsible for idle mode UEtracking and paging procedure including retransmissions as well asbearer activation/deactivation process among other functions. Forexample, the MME 940 may verify authorization of the UE 960 to camp on aservice provider's Public Land Mobile Network (“PLMN”), may enforce UEroaming restrictions, provide control plane function for mobilitybetween LTE and 2G/3G access networks, etc. Of course, as the SAEnetwork architecture is not finalized yet, variations of the systemembodied in FIG. 9 are envisioned and any claims appended herewithshould not be so limited.

TABLE 2 Parameter Range/Type Comment Uplink E-UTRA Absolute Radio0-65535 Section 5.7.3 of 3GPP TS Frequency Channel Number (EARFCN),36.101 V8.5.1. N_(UL) Can be derived from N_(DL) Downlink E-UTRAAbsolute Radio 0-65535 Section 5.7.3 of 3GPP TS Frequency Channel Number(EARFCN), 36.101 V8.5.1. N_(DL) ul-Bandwidth Broadcast in SystemInformation Block(SIB) Section 6.3.1. of 3GPP TS 36.331 V8.4.1. CellIdentity 0-503 SIB2 section 6.2.2. of 3GPP TS 36.331 V8.4.1.UL-CyclicPrefixLength Enumerated RadioResourceConfigCommon message,section 6.3.2 of 3GPP TS 36.331 V8.4.1. srsBandwidth Configuration 0-7SoundingRsUl-Config srsSubframeConfiguration 0-15 message, section 6.3.2of srsBandwidth, b 0-3 3GPP TS 36.331 V8.4.1. frequencyDoinainPosition,Parameter: n_(RRC) 0-23 srsHoppingBandwidth, Parameter: b_(hop) 0-3duration Boolean cyclicShift, Parameter: n_(SRS) 0-7 transmissionComb,Parameter: k_(TC) 0-1 srs-Configurationlndex, Parameter: I_(SRS) 0-1023SoundingRsUl-Config message, section 6.3.2 of 3GPP TS 36.331 V8.4.1.Defined in Section 8.2 of 3GPP TS 36.213 V8.4.0.

With continued reference to FIG. 9, a location service request may beinitiated from the UE 960 at step 901 which may then be provided to thee-SMLC/SMLC 930. In the event that a location service request isinitiated from the e-SMLC/SMLC 930 or other entity, a similar proceduremay be followed to obtain a location for the UE 960. For example, when alocation request service is initiated from an SMLC/e-SMLC 930, theentity may request the serving e-NodeB 950 to send a command to the UE960 at step 903. The command may be utilized to configure or maydirectly configure the UE's SRS transmission pattern at step 904. TheSRS transmitted (step 917) from the UE 960 may be transmitted atspecific or predetermined sub frames and/or with specific orpredetermined characteristics as a function of the configuration messageor command and may be transmitted until the e-NodeB 950 transmitsanother command to the UE 960 to cease transmissions or resettransmissions to an original state (step 916).

The e-NodeB 950 may collect the UE's OTDOA and timing advancemeasurements at step 908 and may transmit these measurements to thee-SMLC/SMLC at step 909. The e-NodeB 950 may also task the LMUs 920 inthe system, directly or via the MME 940 and/or e-SMLC/SMLC 930 (steps905-906) to perform or make uplink and/or downlink measurements at step907 as a function of tipping information. The LMUs 920 may then measureand/or provide uplink TOA measurements to the e-SMLC/SMLC 930 at steps911 and 912. The e-SMLC/SMLC 930 or any position determination equipment(“PDE”) thereof may then determine the location of the UE 960 using anyone or combination of these uplink TOAs, downlink OTDOAs, and timingadvances at step 913. The uplink TOA values may be independently usedfor UE location determination or may be used with the othermeasurements, e.g., OTDOA of neighboring base stations downlink signals,timing advance of the UE, etc.

The e-SMLC/SMLC 930 may then transmit a signal or message to the MME 940that the location request is complete and may transmit the UE positionto the UE 960 or requesting entity via the MME 940 and/or e-NodeB 950 asappropriate (steps 914-915). In one embodiment, the LMU 920 may acquiredownlink frame synchronization and/or sub frame synchronization (step910) to minimize a search window for SRS sequences transmitted from theUE 960. The LMUs 920 may decode the System Frame Number (“SFN”) from thedownlink Master Information Block and determine the precise sub framesthat the SRS sequences are transmitted from the UE 960 based onsrs-ConfigurationIndex I_(SRS) and SRS sub frame offset T_(offset).These parameters are defined in section 8.2 of 3GPP TS 36.101 V.8.5.1the entirety of which is incorporated herein by reference.

A minimum selectable bandwidth for SRS transmission may generally be 48subcarriers (720 kHz) and the periodicity of SRS may be configured to beapproximately 2 ms or more. Embodiments of the present subject mattermay also provide a capability to control periodicity thus allowing aservice provider with greater flexibility to gather several measurementsbased on the nature of location request. The minimum bandwidth of theSRS should provide correlation lobes for proper timing detection withaccuracies within the required boundaries. Enhanced accuracy may also beobtained as a function of higher bandwidths. The setting of the UETransmit power P_(SRS) for the SRS transmitted on sub frames may bealtered by the e-NodeB 950 during a location service request, ifnecessary, for improved detection at the LMU 920.

The SRS may utilize a frequency-domain reference signal sequence derivedas a cyclic extension of prime length Zadoff-Chu sequence. Differentphase rotations may be employed to generate different SRS orthogonal toeach other. By assigning a different phase shift to a differentterminal, multiple SRS can thus be transmitted in parallel in the samesub frame. Hence, several UEs 960 initiating E-911 calls may utilize thesame time-frequency resource grid for location purposes. This is yetanother advantage provided by embodiments of the present subject matterto wireless service providers in the efficient utilization of radioresources for location services without impacting the capacity of maintraffic bandwidth.

As discussed above, uplink measurements may also be made using DMRSsequences. DMRS sequences are generally transmitted for coherentmodulation of the Physical Uplink Shared Channel (“PUSCH”) which carriestraffic data. Using a model or exemplary transmission as a VoIP call,one VoIP packet may be transmitted with one or more Resource Blocks(“RB”) within one transmission timer interval (“TTI”). In LTE, a 1 msTTI generally provides two 0.5 ms slots. The DMRS may be transmitted oneach slot over the 1 ms sub frame. Typically for active users, a VoIPpacket may be received from speech CODEC every 20 ms; thus, a new VoIPtransmission may occur at every 20 TTIs. During inactive periods, aSilence Insertion Descriptor (“SID”) packet may arrive every 160 ms.Uplink TOA measurement, during an E-911 call or other location basedservice request, may require configuration of a VoIP transmission suchthat signals may be properly acquired at an LMU. According to the LTEspecifications, the bandwidth of the DMRS signal is generally equal tothe bandwidth allocated for the PUSCH. A typical VoIP call having 12.2kbps AMR CODEC may require at least 2-3 RB (360 KHz-540 KHz) to transmitspeech packets. Hence, the span of the DMRS in the frequency domain maybe approximately 360 KHz to 540 KHz. This amount of resource allocation,however, may be insufficient to obtain high accuracy uplink timing fromthe DMRS. Embodiments of the present subject matter may employ a DMRSbandwidth of approximately 1 MHz, more or less, and may occupy 72subcarriers and/or 6 RBs in the frequency domain for greater accuracy.In areas having a constrained bandwidth or having limited power, a DMRSwith a bandwidth smaller that 1 MHz may be utilized for locationmeasurements but with less accurate results.

When an E-911 call originates, embodiments of the present subject mattermay allocate a UE with a persistent time-frequency resource so that theUE may transmit DMRS having a predetermined bandwidth and/or TTI for theduration of the respective location measurement process. For persistentscheduling, the characteristics for the DMRS, defined in section 5.5.2.1of 3GPP TS 36.212 V8.4.0 the entirety of which is incorporated herein byreference, may be made constant over the duration of the measurement aswell. Persistent scheduling may be simpler to implement for E-911 callsand may also require less signaling overhead between network entities.

FIG. 10 is a sequence diagram of another embodiment of the presentsubject matter. With reference to FIG. 10, when a location servicerequest is made (step 1001), an e-NodeB 1050 may adopt any one orcombination of the following for uplink scheduling grant assignment:allocation of approximately 6 or more RB when an E-911 or locationrequest is made; schedule the RB under persistent allocation, ascheduling provision within the LTE protocol; grant uplink resourceunder persistent scheduling for a predetermined number of sub-framesrequired to determine location measurements of the target UE. While FIG.10 provides a general illustration of the call flow for a locationservice request initiated from the UE 1060 which may then be provided tothe e-SMLC/SMLC 1030 via an MME 1040, a location service request may beinitiated from the e-SMLC/SMLC 1030 or other entity and a similarprocedure may be followed to obtain a location for the UE 1060.

Upon receipt or initiation of a location request service, theSMLC/e-SMLC 1030 or other entity may request the serving e-NodeB 1050 tosend a command or request to the UE 1060 at step 1003. This request orcommand may be utilized to configure or may directly configure the UE'sDMRS transmission pattern at step 1004 and/or may assign a PUSCH forlocation purposes. The DMRS transmitted (step 1017) from the UE 1060 maybe transmitted with specific or predetermined characteristics discussedabove.

The e-NodeB 1050 may collect the UE's OTDOA and timing advance (“TA”)measurements at step 1008 and may transmit these measurements to thee-SMLC/SMLC 1030 at step 1009. The e-NodeB 1050 may also task the LMUs1020 in the system, directly or via the MME 1040 and/or e-SMLC/SMLC 1030(steps 1005-1006) to perform or make uplink and/or downlink measurementsat step 1007 as a function of tipping information. The LMUs 1020 may betipped with any one or combination of the characteristic informationprovided in Table 3 below from the e-SMLC/SMLC 1030 or GCS. The LMUs1020 may then measure and/or provide uplink TOA measurements to thee-SMLC/SMLC 930 at steps 1011 and 1012. The e-SMLC/SMLC 1030 or anyposition determination equipment (“PDE”) thereof may then determine thelocation of the UE 1060 using any one or combination of these uplinkTOAs, downlink OTDOAs, and timing advances at step 1013. The uplink TOAvalues may be independently used for UE location determination or may beused with the other measurements, e.g., OTDOA of neighboring basestations downlink signals, TA of the UE, etc.

The e-SMLC/SMLC 1030 may then transmit a signal or message to the MME1040 that the location request is complete and may transmit the UEposition to the UE 1060 or requesting entity via the MME 1040 and/ore-NodeB 1050 as appropriate (steps 1014-1015). The LMU 1020 may thusdetermine uplink TOA information by detecting the DMRS signal at the LMU1020. It should be noted, however, that FIG. 10 assumes that there is nodirect interface between an e-NodeB 1050 and the e-SMLC/SMLC 1030. Datamay be passed through an MME 1040 thereby using the MME 1040 as a proxyserver. Of course, the MME 1040 provides additional functionality for anLTE network as previously mentioned. As the SAE network architecture isnot finalized yet, variations of the system embodied in FIG. 10 areenvisioned and any claims appended herewith should not be so limited.

TABLE 3 Parameter Range/Type Bits Uplink E-UTRA Absolute 0-65535 Section5.7.3 of 3GPP TS Radio Frequency Channel 36.101 V8.5.1. Number (EARFCN),N_(UL) Can be derived from N_(DL) Downlink E-UTRA 0-65535 Section 5.7.3of 3GPP TS Absolute Radio Frequency 36.101 V8.5.1. Channel Number(EARFCN), N_(DL) ul-Bandwidth — Broadcast in System InformationBlock(SIB) Section 6.3.1. of 3GPP TS 36.331 V8.4.1. Cell Identity 0-503SIB2 section 6.2.2. of 3GPP TS 36.331 V8.4.1. UL-CyclicPrefixLengthEnumerated RadioResourceConfigCommon message, section 6.3.2 of 3GPP TS36.331 V8.4.1. groupHoppingEnabled Boolean UL-ReferenceSignalsPUSCHgroupAssignmentPUSCH 0-29 message, section 6.3.2 ofsequenceHoppingEnabled Boolean 3GPP TS 36.331 V8.4.1. CyclicShift 0-7Cyclic shift for DM RS 0-7 Cycle shift in DCI format 0 passed to UE atuplink grant, section 5.3.3.1.1 of 3GPP TS 36.212 V8.4.0. Resource BlockCombination DCI format 0 passed to UE at Assignment Structure uplinkgrant, section 5.3.3.1.1 of 3GPP TS 36.212 V8.4.0.

In one embodiment, the LMU 1020 may acquire downlink framesynchronization and/or sub frame synchronization (step 1010) to minimizea search window for DMRS sequences transmitted from the UE 1060. TheLMUs 1020 may decode the SFN from the downlink Master Information Blockand estimate a search window for the DMRS as a function of the uplinkgrant of the radio resource assigned to the UE 1060.

Thus, embodiments of the present subject matter may utilize time-domaincorrelation and/or frequency domain correlation of the Zadoff-ChuReference Sequence (used in SRS and DMRS) at the LMU for detection ofthe SRS or DMRS to obtain uplink TOA measurements. A time domain pilotreplica of the appropriate reference sequence may be generated at theLMU to correlate with the received time domain signal. Once coarsetiming is obtained, the respective signals may be provided to an FFTchannelizer block for fine timing acquisition. Both coherent and noncoherent integration may be applied in both time and frequency domainsto improve detection in sites having a low signal to noise ratio.

FIG. 11 is a diagram of another embodiment of the present subjectmatter. With reference to FIG. 11, a method 1100 is provided forestimating a location of a wireless device receiving signals from pluralnodes of a communications network, such as an LTE network. The pluralnodes may or may not be synchronized as a function of informationreceived from a satellite signal or from a component of thecommunications network.

The method 1100 may include directing a wireless device to transmit afirst signal having one or more predetermined parameters at step 1110,and transmitting the first signal by the wireless device at step 1120.The first signal may be an SRS or DMRS, and the predetermined parametersmay be periodicity, frequency bandwidth, power bandwidth, phaserotation, phase, shift, TTI, and combinations thereof. Anotherembodiment may include the step of acquiring downlink frame or sub-framesynchronization to estimate a search window for the first signal. In afurther embodiment, step 1110 may further comprise transmitting arequest to one or more of the plural nodes to configure the transmissionpattern of the wireless device, and transmitting a second signal fromone or more of the plural nodes to the wireless device in response tothe transmitted request.

At step 1130, an uplink TOA measurement may be determined at one or moreLMUs, the measurement being between the wireless device and one or moreof the plural nodes or LMUs as a function of the transmitted firstsignal. Any of the LMUs may or may not be co-located with a node.Downlink signal measurements of signals received by the wireless devicemay also be collected at step 1140, and a location of the wirelessdevice determined as a function of the uplink TOA measurements and thecollected downlink signal measurements at step 1150. Collected downlinksignal measurements may be, but are not limited to, a range of thewireless device from a serving node, an OTDOA measurement of a signalfrom one or more of the plural nodes, a transmission time of a signalfrom one or more of the plural nodes, a timing advance, a timingadjustment, and combinations thereof. Additional steps may includereceiving a location service request for a wireless device andtransmitting a request to an SMLC for network assistance to locate thewireless device.

FIG. 12 is a diagram of a further embodiment of the present subjectmatter. With reference to FIG. 12, a method 1200 is provided forestimating a location of a wireless device receiving signals from pluralnodes of a communications network, such as an LTE network. The pluralnodes may or may not be synchronized as a function of informationreceived from a satellite signal or from a component of thecommunications network. The method 1200 may include directing a wirelessdevice to transmit an SRS or DMRS with one or more predeterminedparameters at step 1210, and transmitting the SRS or DMRS by thewireless device at step 1220. The predetermined parameters may beperiodicity, frequency bandwidth, power bandwidth, phase rotation,phase, shift, TTI, and combinations thereof. Another embodiment mayinclude the step of acquiring downlink frame or sub-framesynchronization to estimate a search window for the SRS or DMRS. In afurther embodiment, step 1210 may further comprise transmitting arequest to one or more of the plural nodes to configure the transmissionpattern of the wireless device, and transmitting another signal from oneor more of the plural nodes to the wireless device in response to thetransmitted request.

At step 1230, an uplink TOA measurement may be determined at one or moreLMUs, the measurement being between the wireless device and one or moreof the plural nodes or LMUs as a function of the transmitted SRS orDMRS. Any of the LMUs may or may not be co-located with a node. Alocation of the wireless device may then be determined as a function ofthe uplink TOA measurements at step 1240. Additional steps may includereceiving a location service request for a wireless device andtransmitting a request to an SMLC for network assistance to locate thewireless device.

FIG. 13 is a diagram of one embodiment of the present subject matter.With reference to FIG. 13, a method 1300 is provided for estimating alocation of a wireless device receiving signals from plural nodes of anLTE communications network. The plural nodes may or may not besynchronized as a function of information received from a satellitesignal or from a component of the communications network. The method1300 may comprise at step 1310 directing a wireless device to transmit afirst signal having one or more predetermined parameters and at step1320, transmitting the first signal by the wireless device. The firstsignal may be an uplink pilot signal, SRS or DMRS, and the predeterminedparameters may be periodicity, frequency bandwidth, power bandwidth,phase rotation, phase, shift, TTI, and combinations thereof. Step 1310may further comprise transmitting a request to one or more of the pluralnodes to configure the transmission patter of the wireless device andtransmitting a second signal from one or more of the plural nodes to thewireless device in response to the transmitted request.

At step 1330, a range of the wireless device from a node serving thewireless device may be determined as a function of information in thetransmitted first signal by determining a timing adjustment from signalstransmitted by the serving node, receiving the transmitted first signaltransmitted by the wireless device at a reference station, correlatingthe received first signal with a reference signal, determining time ofarrival information from the correlated signal, and determining a rangeof the wireless device from one or more of the plural nodes as afunction of one or more of the time of arrival and timing adjustmentinformation. Any of the reference stations may or may not be co-locatedwith a node. At step 1340, a location of the wireless device as afunction of the determined range. Additional steps may include receivinga location service request for a wireless device and transmitting arequest to an SMLC for network assistance to locate the wireless device.

In a system employing a CDMA2000 communications network, a locationsolution may be similar to that of the UMTS solution described above. Insuch a network, the CDMA base stations may be synchronized using signalsfrom satellites or from a component in the network. The mobile appliancemay then utilize the serving cell's signal as its own timing reference(see section 1.3 of TIA/EIA IS-2000.2-A-1 the entirety of which isincorporated herein by reference). Since the uplink scrambling code isgenerally a function of a mobile appliance's ESN, any detected uplinksignal may provide an opportunity to determine an estimation of thesignal propagation time from the serving site to the mobile applianceand back to the LMU or base station. This information may then beconverted into range rings and hyperbolas.

In one embodiment of the present subject matter, a mobile appliance mayperform the necessary OTDOA measurements and report the measurements toone or more base stations in an exemplary CDMA network, such as aCDMA2000 network. The measurement report message is commonly known asthe Provide Pilot Phase Measurement (see section 3.2.4.2 of 3GPP2C.S0020-0 v3.0 the entirety of which is incorporated herein byreference). OTDOA measurements reported by the mobile appliance mayprovide, for example, mobile appliance system time offset(MOB_SYS_T_OFFSET), measured pilot phase (PILOT_PN_PHASE), and otheruseful parameters. The range, however, is unknown to the mobileappliance at this stage. Once the one or more base stations receive theOTDOA measurements from the mobile appliance, an estimate of the mobileappliance's range therefrom (e.g., a serving base station) may bedetermined utilizing UL TOA information and/or MOB_SYS_T_OFFSETinformation, etc., if available. If the neighboring base station'stiming, which can be expressed in PN offset, is known, the mobileappliance's ranges from the neighboring base stations may also beestimated at this point.

Although only MOB_SYS_T_OFFSET and PILOT_PN_PHASE parameters of theProvide Pilot Phase Measurement message have been identified, suchexamples should not limit the scope of the claims appended herewith asany number or combination of the following parameters of the sameProvide Pilot Phase Measurement message may also be utilized forlocation computation: time of validity of the reported parameters(TIME_REF_MS), reference PN sequence offset (REF_PN), reference pilotsignal strength (REF_PILOT_STRENGTH), number of pilots in measurement(NUM_PILOTS_P), pilot signal strength (PILOT_STRENGTH), and RMS error inPN phase measurement (RMS_ERR_PHASE).

Generally, the OTDOA technique in CDMA2000 is known as Advanced ForwardLink Trilateration (“AFLT”); however, there is an inherent problem withthe AFLT scheme: the forward link transmit time synchronizationgenerally is not accurate enough for good location estimation, Accordingto sections 4.3.1.1 and 4.3.1.1.3 of 3GPP2 C.S0010-0, the downlink pilottime alignment error can be as high as 10 μs, which equates to around ±3km error in range estimation. Although most base station equipmentsynchronizes the downlink pilot timing within 3 μs, the ±900 m rangeerror still poses a problem in location estimation. If, however, LMUsare deployed that measure timing within 25 ns (±7.5 m) (one per basestation or sparsely deployed) in the system, the information in theProvide Pilot Phase Measurement message may be utilized to deriveaccurate range rings. Therefore, the LMUs may make uplink TOAmeasurements for a UL measurement based location solution and may alsocollect downlink samples and perform downlink pilot measurements.

In one embodiment of the present subject matter, the reference basestation may estimate the range to the mobile appliance accurately if theparameter MOB_SYS_T_OFFSET is included in the measurement report.According to section 6.1.5 of ANSI/TIA/EIA-95-B, the entirety of whichis incorporated herein by reference, this offset may be up to ±1 μs(±300 m) in steady state and may be up to 512 chips (±125 km), innon-steady state. If MOB_SYS_T_OFFSET parameter is unavailable, thisoffset will introduce error in range estimation. This error in rangeestimation, however, may be reduced or tracked out using thetriangulation techniques described in co-pending application Ser. No.12/292,821 the entirety of which is incorporated herein by reference.

FIG. 14 is an illustration of one embodiment of the present subjectmatter. With reference to FIG. 14, an exemplary CDMA wirelesscommunication system is shown having three base stations 1400 andassociated antennas 1401. Each base station 1400 may be connected to amobile switching center 1430 which in turn is connected to a PSTN 1440.One embodiment may include a network overlay having plural wirelesslocation sensors 1480 or LMUs with associated antennas 1481 connected toa geolocation processor (or GCS) 1490. The network may collect OTDOAmeasurements from a mobile appliance 1450 and send them to the GCS 1490(or SMLC). The LMUs may or may not be involved with this activity. TheLMUs may also perform UL and DL measurements and send them to theGCS/SMLC 1490. In this embodiment, the GCS/SMLC 1490 may combine theresults, apply LMU measured DL synchronization correction (ifnecessary), convert the measurements into range rings, and compute alocation of the mobile appliance 1450. In another embodiment, the LMU atthe serving site may estimate another range using UL and DL measurementswithout using MOB_SYS_T_OFFSET, as described in co-pending applicationSer. No. 11/984,207, the entirety of which is incorporated herein byreference. The network overlay may be independent of the infrastructureor the wireless communication system. A priori known information such asthe ESN for mobile appliances of interest are generally known by thesystem. Integration into the base station infrastructure is however notprecluded for other practical purposes.

The wireless location sensors or LMUs may be at different locations asshown in FIG. 14 or co-located with the base stations utilizing commontowers or other shared components. In one embodiment of the presentsubject matter, a location of a mobile appliance may be determined usinga reverse pilot channel. The particulars of an exemplary method arecontained in commonly assigned U.S. Pat. No. 7,429,914, the entirety ofwhich is incorporated herein by reference. For example, a target mobileappliance may transmit a reverse pilot signal over a reverse pilotchannel. This reverse pilot signal may be in accordance with IS2000 ormay be any other type of coded signal which represents a uniquesignature that can be discerned independent of traffic signals (e.g.,signals in which voice information is transferred). The reverse pilotsignal may then be received at one or more sensors and correlated with areference signal (typically at a GCS). The reference signal may begenerated as described in U.S. Pat. No. 7,429,914 or other method knownto one of skill in the art. The correlation provides a series ofcorrelation values which, if above a threshold, indicates detection ofthe target mobile appliance's reverse pilot signal. For example,detection of the reverse pilot signal may be accomplished by complexcorrelating the received signal with an internally generated referencesignal of the pilot signal that has been complex scrambled by the targetmobile appliance's unique long code sequence. The location of the peakof the correlation may indicate a TOA of the signal at each sensor orreceiver site. As is known in the art, complex correlation, correlationand cross-correlation all generally refer to processes in the timedomain. One approach to detection is to process the reverse pilot signalusing an ambiguity function which jointly operates in the time andfrequency domains. This approach may allow detection and TOA estimationin the presence of a frequency difference between the reverse pilotsignal and the reference which can occur due to Doppler effects anddifferences in local frequency references. In the event that the sensorsor LMUs are synchronized within the respective system, TDOAs may also bedetermined as appropriate. Therefore, an embodiment of the presentsubject matter may determine an estimate of the location of the targetmobile appliance as a function of any one or combination of range ringsfrom the base stations determined from downlink OTDOA measurements, arange of the mobile appliance from the serving BS from uplinkmeasurements, uplink TOA from the LMU measurements, and hyperbolas andrange rings for neighboring base stations from LMU measurements.

FIG. 15 is a diagram of another embodiment of the present subjectmatter. With reference to FIG. 15, a method 1500 is illustrated forestimating a location of a wireless device receiving signals from pluralnodes of a Code Division Multiple Access 2000 communications system. Theplural nodes may be synchronized as a function of information receivedfrom a satellite signal or may be synchronized as a function ofinformation received from a component of the system, such as, but notlimited to an NSU adaptable to apply a downlink synchronizationcorrection in a respective system. At step 1510, the method may includedetermining one or more ranges of a wireless device from one or more ofthe plural nodes as a function of signals received at the wirelessdevice from the respective one or more plural nodes and as a function ofinformation in an uplink pilot signal. In one embodiment, step 1510 mayfurther include determining one or more ranges of a wireless device fromone or more of the plural nodes as a function of any one or combinationof the following parameters mobile appliance system time offset(MOB_SYS_T_OFFSET), measured pilot phase (PILOT_PN_PHASE), time ofvalidity of the reported parameters (TIME_REF_MS), reference PN sequenceoffset (REF_PN), reference pilot signal strength (REF_PILOT_STRENGTH),number of pilots in measurement (NUM_PILOTS_P), pilot signal strength(PILOT_STRENGTH), RMS error in PN phase measurement (RMS_ERR_PHASE). Inanother embodiment, step 1510 may also include receiving downlinksignals from the one or more plural nodes at the wireless device,reporting time and distance measurements to the system as a function ofthe received downlink signals, and generating one or more range rings asa function of the reported time and distance measurements andinformation in an uplink pilot signal.

Step 1510, in yet another embodiment, may include receiving an uplinkpilot signal transmitted by the wireless device, correlating thereceived uplink pilot signal with a reference signal, determining timeof arrival information from the correlated signal, and determining therange of the wireless device from the serving node as a function of thetime of arrival information. A further embodiment of the present subjectmatter may incorporate the steps of receiving an uplink pilot signaltransmitted by the wireless device, correlating the received uplinkpilot signal with a reference signal, determining time of arrivalinformation from the correlated signal, performing a measurement ofinformation in a downlink pilot signal, and determining the range of thewireless device from the serving node as a function of the time ofarrival information and the downlink pilot measurement information instep 1510. Yet another embodiment of step 1510 may include theadditional step of compensating the determined range as a function ofany one or combination of the following parameters: mobile appliancesystem time offset (MOB_SYS_T_OFFSET), measured pilot phase(PILOT_PN_PHASE), time of validity of the reported parameters(TIME_REF_MS), reference PN sequence offset (REF_PN), reference pilotsignal strength (REF_PILOT_STRENGTH), number of pilots in measurement(NUM_PILOTS_P), pilot signal strength (PILOT_STRENGTH), RMS error in PNphase measurement (RMS_ERR_PHASE), and combinations thereof.

At step 1520, from one or more LMU measurements an uplink time ofarrival (“TOA”) measurement from the device may be determined. TheseLMUs may or may not be co-located with a node. At step 1530, a locationof the wireless device may then be estimated as a function of the uplinkTOA and the determined one or more ranges. In one embodiment, step 1520may also include detecting a signal from the wireless device,determining signal propagation time information from the serving nodeand the wireless device and back to the serving node or an LMU, anddetermining range or time difference of arrival measurements as afunction of the determined information. In a further embodiment of thepresent subject matter, step 1520 may include the additional step ofcompensating the determined range or TDOA measurements as a function ofany one or combination of the following parameters: mobile appliancesystem time offset (MOB_SYS_T_OFFSET), measured pilot phase(PILOT_PN_PHASE), time of validity of the reported parameters(TIME_REF_MS), reference PN sequence offset (REF_PN), reference pilotsignal strength (REF_PILOT_STRENGTH), number of pilots in measurement(NUM_PILOTS_P), pilot signal strength (PILOT_STRENGTH), RMS error in PNphase measurement (RMS_ERR_PHASE), and combinations thereof.

FIG. 16 is an illustration of an exemplary hybrid location techniqueaccording to one embodiment of the present subject matter. Withreference to FIG. 16, an exemplary communications system may includethree BSs 1610, 1612, 1614. BS 1610 is the base station serving a mobileappliance 1620 and BSs 1612, 1614 are the neighboring base stations. Inthis example, at time t₁, the mobile appliance 1620 may hear signalstransmitted from BSs 1610, 1612 and perform downlink OTDOA measurementson these signals. Two range rings 1630, 1632 and a hyperbola 1640 may bederived from these OTDOA measurements. Any two of these three curves orsurfaces are independent and may be utilized for location determinationof the mobile appliance 1620. Similarly, at time t₂, which may or maynot be different than t₁, any LMUs (co-located or otherwise) (not shown)may have made uplink TOA measurements from signals transmitted by themobile appliance 1620. In this non-limiting example, it may be assumedthat the range information or the timing adjustment or advance may beavailable at or around time t₂. The downlink channel condition at timet₁ and uplink channel condition at time t₂ may be different due tomobile movement, different operating frequency, and environmentalvariations. In this non-limiting example, it may also assumed that theLMUs at BSs 1610, 1614 can detect the uplink signal and make TOAmeasurements. Two range rings 1650, 1652 and a hyperbola 1660 may thenbe derived from these LMU measurements. Any two of these three curvesare independent and may then be utilized for location determination ofthe mobile appliance 1620. An exemplary method according to embodimentsof the present subject matter may utilize any combination of the fourrange rings and two hyperbolas to determine the mobile appliance'slocation. Thus, if the OTDOA measurements include a range of the mobileappliance 1620 from the serving site 1610, range rings for all theneighboring sites 1612, 1614 may be computed. Similarly, if the mobileappliance's transmit time, range from the serving site 1610, or thetiming advance (TA) parameter is known, uplink TOA measurements made bythe LMUs may also provide the range rings. Moreover, any TDOAmeasurement, uplink or downlink, may generally provide a hyperbola; andthus, any combination of range rings and hyperbolas may be utilized todetermine the location of the mobile appliance 1620 in embodiments ofthe present subject matter.

It should be noted that the LMU measurements and the downlink OTDOAmeasurements do not have to be performed simultaneously. For example, ifthe mobile appliance is static or stationary, measurements made atdifferent times may be as useful for hybrid location technique as themeasurements made at the same time.

In the event that a target mobile appliance does not support an OTDOAfeature or if the OTDOA measurements are unavailable, the mobileappliance may be located using the LMU measurements alone. Sectorgeometry is often helpful if the number of participating sites is lessthan three. In the event that LMUs are not installed in the network orthe LMU measurements are unavailable, the mobile appliance may belocated using the OTDOA measurements alone. If both the OTDOA and LMUmeasurements are available, an exemplary hybrid location methodaccording to an embodiment of the present subject matter may beexploited to improve the yield and accuracy of the determined locationof the mobile appliance; therefore, in the above example, a hybridapproach may provide three independent range rings which canunambiguously determine the location of the MS.

As shown by the various configurations and embodiments illustrated inFIGS. 1-16, a system and method for hybrid location in a UMTS networkhave been described.

While preferred embodiments of the present subject matter have beendescribed, it is to be understood that the embodiments described areillustrative only and that the scope of the invention is to be definedsolely by the appended claims when accorded a full range of equivalence,many variations and modifications naturally occurring to those of skillin the art from a perusal hereof.

1. A method for estimating a location of a wireless device receivingsignals from plural nodes of a Universal Mobile TelecommunicationsSystem (“UMTS”) network, the method comprising: (a) collecting observedtime difference of arrival (“OTDOA”) measurements of signals received bythe wireless device; (b) transmitting a message to a stand alone servingmobile location center (“SAS”), the message including round trip timeinformation, tipping information, and the collected OTDOA measurements;(c) tasking one or more location measurement units (“LMU”) to determineuplink and downlink signal measurements between the wireless device andones of the plural nodes as a function of the transmitted message; (d)determining at the one or more LMUs range measurements from the wirelessdevice to ones of the plural nodes, uplink time of arrival (“TOA”)measurements, and downlink TOA measurements; and (e) estimating alocation of the wireless device as a function of the uplink and downlinkTOA measurements, OTDOA measurements, round trip time information, andrange measurements.
 2. The method of claim 1 wherein the step ofcollecting OTDOA measurements and the determination of uplink TOAmeasurements are conducted substantially simultaneously.
 3. The methodof claim 1 wherein the message to the SAS is transmitted from a servingradio network controller (“SRNC”).
 4. The method of claim 1 wherein thesteps of collecting OTDOA measurements and transmitting a message to theSAS are performed substantially simultaneously.
 5. The method of claim 4wherein the tipping information in the message is transmitted as theOTDOA measurements are collected.
 6. The method of claim 1 wherein thestep of collecting further comprises determining an OTDOA hyperbolausing information received from a network measurement report.
 7. Themethod of claim 1 wherein the wireless device is selected from the groupconsisting of: cellular device, text messaging device, computer,portable computer, vehicle locating device, vehicle security device,communication device, and wireless transceiver.
 8. The method of claim 1wherein the one or more nodes are selected from the group consisting of:base stations, base station sectors, radio network controllers, servingradio network controllers, and combinations thereof.
 9. The method ofclaim 1 wherein the range measurements are determined as a function of aUE Rx-Tx time difference.
 10. The method of claim 1 further comprisingthe step of transmitting a request for network assistance to at leastone of the plural nodes to locate the wireless device.
 11. A system forestimating a location of a wireless device comprising: (a) circuitry forcollecting observed time difference of arrival (“OTDOA”) measurements ofsignals received by the wireless device; (b) a transmitter fortransmitting a message including round trip time information, tippinginformation, and the collected OTDOA measurements; (c) circuitry fortasking one or more location measurement units (“LMU”) to perform uplinkand downlink signal measurements between the wireless device and ones ofplural nodes as a function of the transmitted message; (d) circuitry atthe one or more LMUs for performing range measurements from the wirelessdevice to ones of the plural nodes, uplink time of arrival (“TOA”)measurements, and downlink TOA measurements; and (e) circuitry forestimating a location of the wireless device as a function of the uplinkand downlink TOA measurements, OTDOA measurements, round trip timeinformation, and range measurements.
 12. The system of claim 11 whereinthe transmitter is located at a serving radio network controller(“SRNC”).
 13. The system of claim 12 further comprising a secondtransmitter for transmitting a request to the SRNC for networkassistance to locate the wireless device.
 14. The system of claim 13wherein the second transmitter is located at a stand alone servingmobile location center (“SAS”).
 15. The system of claim 11 wherein thecircuitry for collecting further comprises circuitry for determining anOTDOA hyperbola using information received from a network measurementreport.
 16. The system of claim 11 wherein the wireless device isselected from the group consisting of: cellular device, text messagingdevice, computer, portable computer, vehicle locating device, vehiclesecurity device, communication device, and wireless transceiver.
 17. Thesystem of claim 11 wherein the one or more nodes are selected from thegroup consisting of: base stations, base station sectors, radio networkcontrollers, serving radio network controllers, and combinationsthereof.